Electric control system



Aug. 11, 1953 w. c. WHITE 2,648,810

ELECTRIC CONTROL SYSTEM Filed Sept. 13, 1951 William Cwhite, by W His Attorney.

Patented Aug. 11, 1953 William 0. White, Schenectady, N.

to General Electric Company,

New York Y., 'assignor I a corporation of Application September 13, 1951, Serial No. 246,460

3 Claims. (01. 321-27) This invention relates to electric control sys" tems and more particularly to a control system for use in conjunction with a plurality of parallel-connected devices, the system being effective to cause conduction of current through a variable number of the devices the actual number being dependent upon the magnitude of a control quantityderived from some variable quantity such as total load current, rate of transfer of energy, or

any desired variable quantity.

Electric devices of the ionizable medium type such'as ignitron type valves, having an anode and a cathode disposed within an enclosing envelope, are particularly adapted for automatic connection or disconnection from service due to the fact that they are readily controlled by controlling the energy supplied to a control electrode. Furthermore, electric valves of the ignitron type do not in general lend themselves to a scaling-up procedure, i. e., the procedure whereby building larger valves decreases their cost per ampere. Thus it is desirable to be able to load a group of para]- lel-connected ignitrons to their maximum output or efficiency and to increase or decrease the number of valves in response to increases or decreases in the magnitude of load. An ignitron valve connected in circuit ready for use but not fired is not using up any more of its useful life than if it is in a storage cabinet.

A principal object of this invention is to provide an improved arrangement for controlling the operation of parallel-connecting electric devices.

Another object of this invention is'the'pro vision of an improved control system for parallelconnected electric valves which causes a number of valves to conduct current dependent upon the magnitude of the current.

Still another object of the invention is to provide an arrangement wherein certain valves are caused to remain nonconductive if the current to be carried is below a predetermined value. Thus a means is provided to make available for instant use tubes which otherwise would be in a spare tube storage cabinet.

In accordance with one form of the invention as applied to parallel-connected ignitrons, each of a plurality of circuits, such as the circuits used for energizing the ignitors of parallel connected ignitron valves, is controlled by a control valve usually a thyratron supplied with a bias of different magnitude. An opposing bias, such as might be dependent upon the magnitude of total load current through the ignitrons, is used to render a number of the control valves conductive thereby to energize'th'eir associated ignitrons.

The invention both as 'to its'organization and method of operation will be better understood from the following description taken in connection with the accompanying drawing in which the singlefigure thereof is a schematic representation'of the invention as applied to a plurality of parallel-connected ignitron valves.

With'reference to the drawing, the alternating current circuit comprising conductors 2 and 3, is interconnected with a direct current circuit comprising conductors 4 and 5 by means'of' a transformer 6 and a'plurality of electric valves -l I. It will beunderstood that the tubes 1-! l" are connected in parallel with eachother and that these valves carry the current from only one phase of the secondar winding of transformer 6 such as the phase 6a. Thus, a similar arrangee ment to that comprising the valves T-l I would be connected to each of the five other windings'of the secondary of transformer B. For simplicity, these additional circuits have been omitted from the drawing.

Each of the valves 1-H is provided with an anode 42, a mercury pool cathode 13, a control element l4 commonly known as an ignito'ryor some other device for initiating the arc cycle by cycle, an auxiliary or holding anode I 5, and a control grid 3. Holding anodes l5 "merely maintain for a desired period a cathode spot established on the cathodes l3 by the action of current through ignitors I4. Since the'circuits for controlling the energization of holding or auxiliary anodes l5 and control grids l6 form no part of the present invention, these have beenomitted from the drawing for the sake of simplicity. Circuits of the tube disclosed in U: S. Patent 2,544,345-Mittag, granted March 6, 1951, or in U. S. Patent 2,517,129-Mulhern, granted August 1, 1950, both of which areassigned to the assignee of this invention, could be used to control the control grids l6 and the auxiliary or holding anodes IS. The cathodes of the valves 1-1 [are all connected to acommon bus l1 while the anodes I 2 of valves 1-H are all connected to a'common bus l8.

Theignitor I4 of valve 1 is connected to a control bus 19 which is energized from a schematically represented ignitor firing circuit 20 which normally would be energized from a source of alternating current.

2,523,027-Kellogg et al., granted Septemberlll, 1950, and assignedto the assignee of this in: vention. V

The ignitors M of the valves 8-H are respec tively connected to the control'bus l9 through Ignitor firing circuit 20 could be of any known type such, for example, i as is disclosed" and claimed in U. '8. Patent;

26 which is energized by any suitable source of:

direct current voltage such as is indicated by. the battery 2?. Connected across potentiometer 26 and battery 2! is a smoothing: capacitor 28,1 Since the terminal 29 of potentiometer. 26 1s. positive: with respect to the terminal 30 thereof, the grids of control valves 2i-2 i are. provided-with pro gressively increasing negative bias from left to right. Thus the negative bias on the grid,.25 of control valve 22 is greater'in magnitude than the negative. bias suppliedto the grid 25 of control alve grid valve is is greater than such bias on the grid of valve. 22, and the negative bias supplied to grid 25 of control valve 24 is greater in magnitude than the negative bias supplied to the grid of controlvalve 23. It will thus, be understood-from, the description thus far that a greater potential is needed to overcome the bias of the valve 22 than is needed to overcome the bias of valve. 2i, for example.

Since the arrangement shown inthe drawing. is.

responsive to variations in load conditions, a current transformer 3| is provided for deriving a signal dependent on the magnitude of current. Transformer Si is provided with a primary winding 32. and a secondary winding 33. Primary winding 32 as will be seen from the drawing isin series with the secondary winding 5a of transformerv 6 and with the parallel connected ignitron valves l-Il. Thus it will be understood that a predetermined magnitude of current through the primary winding 32 will derive a predetermined magnitude of'voltage which when applied to the potentiometer 26 can be sufficient to overcome the negative bias on the grid. 25 of valve 2|. Should the load current increase through the primary winding 32 of transformer 3|, the signal derived by the secondary wind-. ing. 33 will be proportionately greater and can be 'su mcient. to. overcome the bias of the grid 2510f valvev 22. Thus it crease in current through transformer 3| will cause a progressively greater number of the control valves '2 5-2 to be rendered conductive so that current circuits t t-Lil which interconnect the valves 2 l-,-,2 4.,with the ignitors M, of the ignitrons. l-.-l L

It will, furthermore, be understood thatthe actionof control valves 21-214 is dependent upon the resultant voltage which is supplied to each of the control circuits 38-41 which in turn is dependent upon the magnitude of current flow. through th transformer 3 l It will be understood that some other meansv than the transformed 3i could be utilized to regulate the number of the ignitrons T-l lwhich are rendered conductive ata particular instant. For. example, it voltage between nitude of current in the direct current conduc-. tors 4 or 5v as. the sourcev for a control signal which would be equivalent to the, transformer 31. position of willdetermine when each tube cutsin or out with change of load.

It will also be understood that my invention is not limited to the use of control valves having control grids such as the devices 21-24; For

Likewise, the negative bias on the may flow through one or more of the Thev the taps on potentiometer resistor 26 will be seen that an in-.

would be possible to utilize the the buses ll and I8, or the mag-..

4 example, a magnetic amplifier or amplistat having main windings and a control winding could be used forthis purpose.

- While I have shown and: described a-particular embodiment of my invention, I do not wish to be limited thereto and intend in the appended claims tocover all such changes and modifications as fall within the true spirit and scope of the inven sm- What I claim: as new and desire to secure by Letters Patent of the United States is:

,...A,. eontrol, system, for a plurality of circuits arranged for traverse 'by current comprising an electric valve connected in each of said circuits, each of said valves having a control grid supplied with a negative bias voltage tending to prevent, the flow ofcurrent therethrough, the magnitude of bias supplied to each control grid being different from the magnitude of bias supplied to every other control grid, and means for simultaneously supplying a variable control volt-M age to each of said control grids, which opposesthe bias voltageof said grids soas to render a,

number of said control valves and their. asso ciated circuits conductive, the number of said,

valves and of said circuits'so rendered conductive being dependent, upon theimagnitude ofsaid variable control voltage.

2. In combinationa plurality of electric devices each having an anode, aJcathode and. a controlv element, said devices havingtheir anode-cathodecircuits connected in parallel between an. alters nating current circuit anda direct current cir cuit, a circuit for. energizing the control elements, of. said. devices, a, separate; control valve inter connected. between, said, circuit, and certain, of said control elements, said control valves. each having a. control grid, said control gridsbeing suppli d with a different negative bias, and means for simultaneously supplying a voltage to said control grids which opposes the negative bias.

supplied toeachof, said control grids, the magt den Said vo ta e be g var a as t ner.

tion of the rateof transfer of energy between s id. alte nat ng c rr nt. cir u t. an said. d r c current circuit.

.3; lnrcmb nationa pl r l of l ct ic devi es. each having an anode, a cathode and a control;

ment, s de ices ha ing. r. anod at qde cu sv c nnected, in parall l b tw n an. terna n r n c r ui nds, d e t'c rr nt ruit, a ircrit. for. nergizin the control e ments of said devices, a separate control valve te conn cted. betw n i i cu nd" c a n o a 'cijcont cl' l m nts s i c n r i lv earthv having a control grid, said control grids being suppli d with a different negative bias, and means for simultaneously supplying a voltage to said;

n rol idswhich. opp the ga bias 51 9-. plied to each of'said'control grids, the magnitude ofsaid voltage being variable as a function th ota curr nt flow n e wee saidialteb mat n urrent. ircuit a ai direct; curren circuit.

WILDIAM o; References. .Cited in the file of this-patent; UNITED" STATES PAT ENTS' Number Name. Date 5 91. K hn. a 31f 1,902,4 0 Mittag Mar. 21, 1933 1337371 Willis NOV. 28,: 1933 2,088,474 Haller July 27,-;193'? 

